Optimal timing of surgery in infective endocarditis (IE) depends mainly on the haemodynamic tolerance of the patient. Emergency surgery is required in cases of refractory heart failure due to valvular lesions, intracardiac fistulas and high grade cardiac conduction abnormalities caused by septal abscesses. Surgery must be considered in all patients who have undergone a transient episode of heart failure such as a pulmonary oedema and it must be early--within 2 or 3 weeks of starting antibiotic therapy in patients with aortic regurgitation. Bacteriological indications are less frequent: persistent sepsis beyond the first week in spite of medical therapy, mycotic IE or prosthetic valve endocarditis caused by Gram-negative or staphylococcal organisms. Some complications may swing the argument in favour of surgery: detection of root abscesses or mycotic aneurysms using transoesophageal echocardiography, and systemic embolisms with persistent, large and mobile vegetative lesions. Mortality rate depends on the haemodynamic status but also on the severity of anatomical lesions, on the type of endocarditis (native or prosthetic valve), on the type of surgery and on bacterial aetiologies. It varies between 5% and 30%. The late postoperative outcome is good. The actuarial survival rate at 8 years was 70% in our series of 31 patients with aortic regurgitation and early surgery. In mitral regurgitation, conservative surgery is possible in most cases. In our department, 48 patients with mitral bacterial lesions have been operated on with conservative surgery without operative mortality. IE was active in 14, recent in 12 and had occurred earlier in 22.(ABSTRACT TRUNCATED AT 250 WORDS)